The subject matter disclosed herein relates to X-ray tubes, and, more specifically, to features for minimizing relative bearing shaft deflection and/or controlling rotor dynamic modes.
A variety of diagnostic and other systems may utilize X-ray tubes as a source of radiation. In medical imaging systems, for example, X-ray tubes are used in projection X-ray systems, fluoroscopy systems, tomosynthesis systems, and computer tomography (CT) systems as a source of X-ray radiation. The radiation is emitted in response to control signals during examination or imaging sequences. The radiation traverses a subject of interest, such as a human patient, and a portion of the radiation impacts a detector or a photographic plate where the image data is collected. In conventional projection X-ray systems the photographic plate is then developed to produce an image which may be used by a radiologist or attending physician for diagnostic purposes. In digital X-ray systems a digital detector produces signals representative of the amount or intensity of radiation impacting discrete pixel regions of a detector surface. In CT systems a detector array, including a series of detector elements, produces similar signals through various positions as a gantry is displaced around a patient.
An anode assembly (or target assembly) generally includes a rotor and a stator outside of the X-ray tube at least partially surrounding the rotor for causing rotation of an anode during operation of the X-ray tube. The anode is supported in rotation by a bearing, which, when rotated, also causes the anode to rotate. The bearing typically includes a shaft and a bearing sleeve disposed about the shaft to which the anode is attached. During operation of the X-ray system, the shaft experiences radial loads (e.g., due to centrifugal forces from the X-ray tube rotating on a CT gantry) along its surface that cause bending moments and relative deflection of the shaft causing the shaft to bend and contact or rub against the bearing sleeve. Over time, the bearing surfaces become worn and fails. The relative deflection of the bearing also reduces the maximum usable eccentricity and limits the load carrying capability of the shaft. In addition, undesirable rotor dynamic modes can also contribute to wear in the shaft.